Improvements in the design of one type of Compton-electron spectrometer for γ-rays are proposed. The design requires a magnetic field of cylindrical symmetry and of slow radial variation, a simply curved radiator, and a system of apertures. Electrons are accepted only if they are ejected from the radiator with small components of momentum in two orthogonal directions perpendicular to the incident γ-ray. Since the magnetic field can also be used to measure the momentum of the selected electrons, the instrument can function as a γ-ray spectrometer. Higher-order aberrations are discussed, and a method of calculating the values of the various spectrometer parameters corresponding to maximum efficiency is given. Calculations of the intrinsic line-width, caused by the motion of the electron within the atom before collision with the photon, are carried out.
The Compton electron beam Polarimeter for the AmPS ring